Nanowire preparation methods, compositions, and articles

ABSTRACT

Methods of producing metal nanowires, compositions, and articles are disclosed. Such methods allow production of metal nanowires with reproducibly uniform diameter and length, even in the presence of catalyst concentration variation. Such metal nanowires are useful for electronics applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/432,615, filed Jan. 14, 2011, entitled NANOWIRE PREPARATION METHODS,COMPOSITIONS, AND ARTICLES; U.S. Provisional Application No. 61/488,811,filed May 23, 2011, entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS,AND ARTICLES; U.S. Provisional Application No. 61/488,814, filed May 23,2011, entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES;and U.S. Provisional Application No. 61/500,155, filed Jun. 23, 2011,entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES, eachof which is hereby incorporated by reference in its entirety.

BACKGROUND

The general preparation of silver nanowires (10-200 aspect ratio) isknown. See, for example, Angew. Chem. Int. Ed. 2009, 48, 60, Y. Xia, Y.Xiong, B. Lim, S. E. Skrabalak, which is hereby incorporated byreference in its entirety. Such preparations typically employ Fe²⁺ orCu²⁺ ions to “catalyze” the wire formation over other morphologies. Thecontrolled preparation of silver nanowires having desired lengths andwidths, however, is not known. For example, the Fe²⁺ produces a widevariety of lengths or thicknesses and the Cu²⁺ produces wires that aretoo thick for many applications. When iron or copper are used, they aretypically provided as the metal halide salts FeCl₂ or CuCl₂. See, forexample, B. Wiley et al., Nano Letters, 2004, 4, 1733-1739 and K. E.Korte et al., J. Mats. Chem., 2008, 18, 437. Other metal halide saltshave been used in nanowire synthesis. See, for example, J. Jiu, K.Murai, D. Kim, K. Kim, K. Suganuma, Mat. Chem. & Phys., 2009, 114, 333,which refers to NaCl, CoCl₂, CuCl₂, NiCl₂ and ZnCl₂, and S, Nandikonda,“Microwave Assisted Synthesis of Silver Nanorods,” M. S. Thesis, AuburnUniversity, Auburn, Ala., USA, Aug. 9, 2010, which refers to NaCl, KCl,MgCl₂, CaCl₂, MnCl₂, CuCl₂, and FeCl₃. Use of KBr has been disclosed in,for example, D. Chen et al., J. Mater. Sci.: Mater. Electron., 2011,22(1), 6-13; L. Hu et al., ACS Nano, 2010, 4(5), 2955-2963; and C. Chenet al, Nanotechnology, 2006, 17, 3933. Use of NaBr has been disclosedin, for example, L. Zhou et al., Appl. Phys. Letters, 2009, 94, 153102.See also S. Murali et al., Langmuir, 2010, 26(13), 11176-83; Z. C. Li etal., Micro & Nano Letters, 2011, 6(2), 90-93; and B. J. Wiley et al.,Langmuir, 2005, 21, 8077.

Japanese patent application publication 2009-155674 discloses use ofSnCl₄. U.S. patent application publication 2010/0148132 discloses use ofNaCl, KCl, CaCl₂, MgCl₂, and ZnCl₂. U.S. patent application publications2008/0210052 and 2011/0048170 disclose use of quaternary ammoniumchlorides.

SUMMARY

At least a first embodiment provides methods comprising providing atleast one compound capable of forming at least one halide ion, where thecompound comprises at least one first atom, at least one halogen atombonded to the at least one first atom, and at least one carbon atombonded to the at least one first atom; and reducing at least one firstmetal ion to at least one first metal in the presence of at least one ofthe at least one compound or the at least one halide ion. In suchmethods, the absolute value of the difference in electronegativities ofthe at least one first atom and the at least one halogen atom may begreater than about 0.4 Pauling units and less than about 2.0 Paulingunits.

In such methods, the at least one first atom may, for example, compriseat least one of a boron atom, a nitrogen atom, a phosphorus atom, asilicon atom, a sulfur atom, a selenium atom, or a carbon atom. Or, insome cases, the at least one first atom may comprise at least one of aboron atom, a phosphorus atom, a silicon atom, or a carbon atom.

In some cases, the at least one halide ion may, for example, comprise atleast one chloride ion, bromide ion, or iodide ion. Or, in some cases,the at least one halide may comprise at least one chloride ion orbromide ion.

In at least some embodiments, the at least one compound may comprise atleast one carbocation. For example, such a carbocation may be a primarycarbocation, a secondary carbocation or a tertiary carbocation.

Non-limiting examples of the at least one compound arediethyldichlorosilane, phenylphosphonic dichloride,dichlorophenylborane, and triphenylchloromethane.

In at least some embodiments, such methods may further comprise formingthe at least one first halide ion by solvolysis of the at least onecompound. Solvolysis may, for example, comprise one or more ofhydrolysis, alcoholysis, glycolysis, acidolysis, aminolysis, orammonolysis.

In at least some cases, the at least one first metal may, for example,comprise at least one element from IUPAC Group 11 or at least onecoinage metal. An exemplary at least one first metal is silver.

Other embodiments provide the at least one first metal produced by suchmethods. Still other embodiments provide nanowires comprising the atleast one first metal produced by such methods.

At least a second embodiment provides methods comprising providing acomposition comprising an amount of at least one organosilicon halidecompound that is capable of forming at least one halide ion; andreducing at least one first metal ion to at least one first metal in thepresence of the composition. The at least one organosilicon halidecompound may, for example, comprise at least one silicon atom bonded toat least one halogen atom, or at least one silicon atom bonded to atleast two halogen atoms. The at least one halide ion may, for example,comprise at least one chloride ion. The at least one first silver metalion may, for example, comprise at least one element from IUPAC Group 11,or at least one coinage metal ion, or at least one silver ion. The atleast one organosilicon halide compound may, for example, comprise asilicon atom bonded to at least one halogen atom, where the silicon atomis also bonded to at least one carbon atom, or it may comprise a siliconatom bonded to at least one halogen atom, where the silicon atom is alsobonded to at least two carbon atoms, or it may, for example, comprisediethyldichlorosilane.

In at least some embodiments, such methods further comprise regulatingthe rate of halide generation by at least one of choosing the at leastone organosilicon halide compound, selecting the amount of the at leastone organosilicon halide compound in the composition, or selecting atleast one temperature at which to perform the reduction.

Other embodiments further provide the at least one first metal productproduced according to such embodiments. Such products may, for example,comprise at least one nanowire.

Still other embodiments further provide articles comprising the at leastone first metal product produced according to such embodiments. Sucharticles may, for example, comprise electronic devices.

At least a third embodiment provides methods comprising providing acomposition comprising at least one compound capable of forming at leastone halide ion, where the compound comprises at least one of a boronatom, a nitrogen atom, a phosphorus atom, a sulfur atom, or a seleniumatom; and reducing at least one first metal ion to at least one firstmetal ion the presence of the composition. The compound may, forexample, comprise at least one first atom bonded to at least one halogenatom and to at least one carbon atom. Such a first atom may, forexample, comprise at least one of a boron atom, a nitrogen atom, aphosphorus atom, a sulfur atom, or a selenium atom. An exemplary atleast one compound is phenylphosphonic dichloride. In at least someembodiments, the at least one halide ion comprises at least one chlorideion. The at least one first metal ion may, for example, comprise atleast one element from IUPAC Group 11, or at least one coinage metalion, such as, for example, a silver ion.

In at least some embodiments, such methods may further compriseregulating the rate of halide generation by at least one of choosing theat least one compound, selecting the amount of the at least one compoundin the composition, or selecting at least one temperature at which toperform the reduction.

In at least some embodiments, the reducing may occur in the presence ofat least one second metal or metal ion that has an atomic numberdifferent from that of the at least one first metal ion.

Other embodiments provide the at least one first metal product producedby such methods. Such a product may, for example, comprise at least onenanowire.

Still other embodiments provide an article comprising the at least onefirst metal product produced by such methods.

At least a fourth embodiment comprises methods comprising providing anamount of at least one organo-halide compound, where the compound iscapable of forming at least one carbocation and at least one halide ionand reducing the at least one first metal ion to at least one firstmetal in the presence of the composition.

In at least some embodiments, the at least one organo-halide compoundmay comprise a carbon atom bonded to at least one halogen atom, and alsoto at least one aromatic ring by at least one carbon-carbon bond. Orsuch a carbon atom may be bonded to at least one halogen atom, and alsoto at least two aromatic rings by at least two carbon-carbon bonds. Orsuch a carbon atom may be bonded to one halogen atom, and also to threearomatic rings by at three carbon-carbon bonds. Such a compound may, forexample, comprise triphenylchloromethane.

In at least some embodiments, the at least one carbocation comprises atleast one secondary carbocation or tertiary carbocation, or the at leastone carbocation comprises at least one tertiary carbocation.

In some cases, the at least one halide ion comprises a chloride ion or abromide ion, or the at least one halide ion comprises at least onechloride ion.

In at least some embodiments, such methods may further compriseregulating the rate of halide generation by at least one of choosing theat least one organo-halide compound, selecting the amount of the atleast one organo-halide compound in the composition, or selecting atleast one temperature at which to perform the reduction.

Other embodiments provide the at least one first metal product producedby such methods. Such a product may, for example, comprise at least onenanowire.

Still other embodiments provide an article comprising the at least onefirst metal product produced by such methods.

These embodiments and other variations and modifications may be betterunderstood from the description of figures, figures, description,exemplary embodiments, examples, and claims that follow. Any embodimentsprovided are given only by way of illustrative example. Other desirableobjectives and advantages inherently achieved may occur or becomeapparent to those skilled in the art. The invention is defined by theappended claims.

DESCRIPTION OF FIGURES

FIG. 1 shows an optical micrograph of the silver nanowire product ofExample 1.

FIG. 2 shows an optical micrograph of the silver nanowire product ofExample 2.

FIG. 3 shows an optical micrograph of the silver nanowire product ofExample 3.

FIG. 4 shows an optical micrograph of the silver nanowire product ofExample 4.

FIG. 5 shows an optical micrograph of the reaction product ofcomparative Example 8.

FIG. 6 shows an optical micrograph of the reaction product ofcomparative Example 9.

FIG. 7 shows an optical micrograph of the reaction product ofcomparative Example 10.

FIG. 8 shows an optical micrograph of the reaction product ofcomparative Example 12.

FIG. 9 shows an optical micrograph of the reaction product ofcomparative Example 13.

FIG. 10 shows an optical micrograph of the reaction product ofcomparative Example 14.

FIG. 11 shows an optical micrograph of the silver nanowire product ofExample 15.

FIG. 12 shows an optical micrograph of the silver nanowire product ofExample 16.

DESCRIPTION

All publications, patents, and patent documents referred to in thisdocument are incorporated by reference herein in their entirety, asthough individually incorporated by reference.

U.S. Provisional Application No. 61/432,615, filed Jan. 14, 2011,entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES; U.S.Provisional Application No. 61/488,811, filed May 23, 2011, entitledNANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES; U.S.Provisional Application No. 61/488,814, filed May 23, 2011, entitledNANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES; and U.S.Provisional Application No. 61/500,155, filed Jun. 23, 2011, entitledNANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES, are eachhereby incorporated by reference in its entirety.

At least some embodiments provide methods employing at least onecompound capable of forming at least one halide ion in the reduction ofmetal ions, where the reduction occurs in the presence of the at leastone compound or the at least one halide ion. Such compounds comprise atleast one first atom bonded to at least one carbon atom and to at leastone halogen atom. The bond between the at least one first atom and theat least one halogen atom may be termed a “polar covalent” bond, whichfor this application is meant in the sense that the absolute value ofthe difference in electronegativities of the at least one first atom andthe at least one halogen atom is greater than about 0.4 Pauling unitsand less than about 2.0 Pauling units. Such methods can allow productionof, for example, metal nanowires that have reproducibly uniformthicknesses and lengths, even in the presence of run-to-run variabilityin the concentration of the at least one compound.

Metal Ions and Metal Products

Some embodiments provide methods comprising reducing metal ions tometal. Such metal ions may be referred to as “reducible metal ions,” inthe sense that that are capable of being reduced to a metal under someset of reaction conditions. In such methods, the metal ion may, forexample, comprise at least one ion of an IUPAC Group 11 element or atleast one coinage metal ion. A coinage metal ion is an ion of one ormore of the coinage metals, which include copper, silver, and gold. Suchmetal ions may, in some cases, be provided as salts. For example, silvercations might, for example, be provided as silver nitrate.

In such embodiments, the at least one metal is that metal to which theat least one metal ion is capable of being reduced. For example, silverwould be the metal to which a silver cation would be capable of beingreduced.

Compounds Comprising Carbon(s), Halogen(s), and Polar Covalent Bond(s)

Some embodiments provide methods comprising reducing metal ions to metalin the presence of at least one compound or halide ion, where thecompound comprises at least one first atom bonded to at least one carbonatom and to at least one halogen atom, where the bond between the atleast one first atom and the at least one halogen atom is a “polarcovalent” bond, which for this application is meant in the sense thatthe absolute value of the difference in electronegativities of the atleast one first atom and the at least one halogen atom is greater thanabout 0.4 Pauling units and less than about 2.0 Pauling units.

Use of such compounds in the reduction of metal ions can allow theprovision of halide ions without also providing catalyst metal cationsor other nonprotic cations. In traditional nanowire synthesis methods,halide ions are provided with catalyst metal cations or other nonproticcations in stoichiometric ratios governed by the identity of thehalogen-bearing compounds. While not wishing to be bound by theory, itis believed that the presence of such cations can affect both theability to form nanowires and the morphology of the nanowires that areformed. The methods and compositions of this application can insteadprovide metal nanowires that have reproducibly uniform thicknesses andlengths, even in the presence of run-to-run variability in theconcentration of the at least one compound.

In such methods, the at least one first atom may, for example, compriseat least one of a boron atom, a nitrogen atom, a phosphorus atom, asilicon atom, a sulfur atom, a selenium atom, or a carbon atom. Or, insome cases, the at least one first atom may comprise at least one of aboron atom, a phosphorus atom, a silicon atom, or a carbon atom.

In some cases, the at least one halide ion may, for example, comprise atleast one chloride ion, bromide ion, or iodide ion. Or, in some cases,the at least one halide may comprise at least one chloride ion orbromide ion.

Non-limiting examples of the at least one compound arediethyldichlorosilane, phenylphosphonic dichloride,dichlorophenylborane, and triphenylchloromethane.

Other non-limiting examples of the at least one compound are compoundswith the following chemical formulae: RxSiX_(y), where x+y=4 and y isnon-zero; compounds R_(x)BX_(y), where x+y=3 and y is not zero;borazines R_(x)B₃N₃X_(y), where x+y=3 and y is non-zero; RxPX_(y), wherex+y=3 and y is non-zero; RxPDX_(y), where x+y=3 and y is non-zero; acidhalides RCOX; R_(x)CX_(y), where x+y=4 and y is non-zero; andR_(x)H_(z)CX_(y), where x+y+z=4, and x and y are non-zero. In theseformulae, X represents a halogen atom and R represents an alkyl group, asubstituted alkyl group, an aryl group, or a substituted aryl group.Substituted alkyl or aryl groups may comprise halogens, alkoxy moieties,amines, and the like.

In at least some embodiments, the at least one compound may be capableof forming at least one carbocation and at least one halide ion. Such acompound may, for example, comprise a carbon atom bonded to at least onehalogen atom, and also to at least one aromatic ring by at least onecarbon-carbon bond; or the compound may, for example, comprise a carbonatom bonded to at least one halogen atom, and also to at least twoaromatic rings by at least two carbon-carbon bonds; or the compound may,for example, comprise a carbon atom bonded to one halogen atom, and alsoto three aromatic rings by at three carbon-carbon bonds. In some cases,such a carbocation may comprise at least one secondary carbocation ortertiary carbocation, or the at least one carbocation comprises at leastone tertiary carbocation. Such a compound may, for example, comprisetriphenylchloromethane.

Solvolysis

In at least some embodiments, such methods may further comprise formingthe at least one first halide ion by solvolysis of the at least onecompound. Solvolysis is a type of nucleophilic substitution where thenucleophile is a solvent molecule. Solvolyis may, for example, compriseone or more of hydrolysis, alcoholysis, glycolysis, acidolysis,aminolysis, or ammonolysis.

In some embodiments, solvolysis may be performed in a reaction mixturethat may, for example, comprise one or more polyols, such as, forexample, ethylene glycol, propylene glycol, butanediol, glycerol,sugars, carbohydrates, and the like.

Solvolysis of the at least one compound can provide halide ions withoutsimultaneously introducing catalyst metal ions or other nonproticcations. Without wishing to be bound by theory, it is believed thatsolvolysis of the polar covalent bond between the at least one firstatom and at least one halogen atom results in production of a halide ionand a proton or protic cation.

By removing the traditional stoichiometric linkage between halide ionsand nonprotic cations, it is possible to reduce metal ions in thepresence of lowered nonprotic cation levels or even with little or nononprotic cations being present.

Nanostructures, Nanostructures, Nanowires, and Articles

In some embodiments, the metal product formed by such methods is ananostructure, such as, for example, a one-dimensional nanostructure.Nanostructures are structures having at least one “nanoscale” dimensionless than 300 nm. Examples of such nanostructures are nanorods,nanowires, nanotubes, nanopyramids, nanoprisms, nanoplates, and thelike. “One-dimensional” nanostructures have one dimension that is muchlarger than the other two nanoscale dimensions, such as, for example, atleast about 10 or at least about 100 or at least about 200 or at leastabout 1000 times larger.

Such one-dimensional nanostructures may, in some cases, comprisenanowires. Nanowires are one-dimensional nanostructures in which the twoshort dimensions (the thickness dimensions) are less than 300 nm,preferably less than 100 nm, while the third dimension (the lengthdimension) is greater than 1 micron, preferably greater than 10 microns,and the aspect ratio (ratio of the length dimension to the larger of thetwo thickness dimensions) is greater than five. Nanowires are beingemployed as conductors in electronic devices or as elements in opticaldevices, among other possible uses. Silver nanowires are preferred insome such applications.

Such methods may be used to prepare nanostructures other than nanowires,such as, for example, nanocubes, nanorods, nanopyramids, nanotubes, andthe like. Nanowires and other nanostructure products may be incorporatedinto articles, such as, for example, electronic displays, touch screens,portable telephones, cellular telephones, computer displays, laptopcomputers, tablet computers, point-of-purchase kiosks, music players,televisions, electronic games, electronic book readers, transparentelectrodes, solar cells, light emitting diodes, other electronicdevices, medical imaging devices, medical imaging media, and the like.

Preparation Methods

A common method of preparing nanostructures, such as, for example,nanowires, is the “polyol” process. Such a process is described in, forexample, Angew. Chem. Int. Ed. 2009, 48, 60, Y. Xia, Y. Xiong, B. Lim,S. E. Skrabalak, which is hereby incorporated by reference in itsentirety. Such processes typically reduce a metal cation, such as, forexample, a silver cation, to the desired metal nanostructure product,such as, for example, a silver nanowire. Such a reduction may be carriedout in a reaction mixture that may, for example, comprise one or morepolyols, such as, for example, ethylene glycol (EG), propylene glycol,butanediol, glycerol, sugars, carbohydrates, and the like; one or moreprotecting agents, such as, for example, polyvinylpyrrolidinone (alsoknown as polyvinylpyrrolidone or PVP), other polar polymers orcopolymers, surfactants, acids, and the like; and one or more metalions. These and other components may be used in such reaction mixtures,as is known in the art. The reduction may, for example, be carried outat one or more temperatures from about 120° C. to about 190° C., or fromabout 80° C. to about 190° C.

EXEMPLARY EMBODIMENTS

U.S. Provisional Application No. 61/432,615, filed Jan. 14, 2011,entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES, whichis hereby incorporated by reference in its entirety, disclosed thefollowing fourteen non-limiting exemplary embodiments:

A. A method comprising:

-   -   providing a composition comprising an amount of at least one        organosilicon halide compound, said compound capable of forming        at least one halide ion; and    -   reducing at least one first metal ion to at least one first        metal in the presence of the composition.        B. The method according to embodiment A, wherein the at least        one organosilicon halide compound comprises at least one silicon        atom bonded to at least one halogen atom.        C. The method according to embodiment A, wherein the at least        one organosilicon halide compound comprises at least one silicon        atom bonded to at least two halogen atoms.        D. The method according to embodiment A, wherein the at least        one halide ion comprises at least one chloride ion.        E. The method according to embodiment A, wherein the at least        one first metal ion comprises at least one element from IUPAC        Group 11.        F. The method according to embodiment A, wherein the at least        one first metal ion comprises at least one coinage metal ion.        G. The method according to embodiment A, wherein the at least        one first metal ion comprises at least one silver ion.        H. The method according to embodiment A, wherein the at least        one organosilicon halide compound comprises a silicon atom        bonded to at least one halogen atom, said silicon atom being        also bonded to at least one carbon atom.        J. The method according to embodiment A, wherein the at least        one organosilicon halide compound comprises a silicon atom        bonded to at least one halogen atom, said silicon atom being        also bonded to at least two carbon atoms.        K. The method according to embodiment A, wherein the at least        one organosilicon halide compound comprises        diethyldichlorosilane.        L. The method according to embodiment A, further comprising        regulating the rate of halide generation by at least one of        choosing the at least one organosilicon halide compound,        selecting the amount of the at least one organosilicon halide        compound in the composition, or selecting at least one        temperature at which to perform the reduction.        M. At least one first metal product produced according to the        method of embodiment A.        N. The at least one first metal product according to embodiment        M, said at least one product comprising at least one nanowire.        P. An article comprising the at least one first metal product        according to embodiment M.

U.S. Provisional Application No. 61/488,814, filed May 23, 2011,entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES, whichis hereby incorporated by reference in its entirety, disclosed thefollowing twelve non-limiting exemplary embodiments:

Q. A method comprising:

-   -   providing a composition comprising at least one compound capable        of forming at least one halide ion, said compound comprising at        least one of a boron atom, a nitrogen atom, a phosphorus atom, a        sulfur atom, or a selenium atom; and    -   reducing at least one first metal ion to at least one first        metal in the presence of the composition.        R. The method according to embodiment Q, wherein the compound        comprises at least one first atom bonded to at least one halogen        atom and to at least one carbon atom.        S. The method according to embodiment R, wherein the at least        one first atom comprises at least one of a boron atom, a        nitrogen atom, a phosphorus atom, a sulfur atom, or a selenium        atom.        T. The method according to embodiment Q, wherein the at least        one compound comprises phenylphosphonic dichloride.        U. The method according to embodiment Q, wherein the at least        one halide ion comprises at least one chloride ion.        V. The method according to embodiment Q, wherein the at least        one first metal ion comprises at least one element from IUPAC        Group 11.        W. The method according to embodiment Q, wherein the at least        one first metal ion comprises at least one coinage metal ion.        X. The method according to embodiment Q, wherein the at least        one first metal ion comprises at least one silver ion.        Y. The method according to embodiment Q, further comprising:    -   regulating the rate of halide generation by at least one of        choosing the at least one compound, selecting the amount of the        at least one compound in the composition, or selecting at least        one temperature at which to perform the reduction.        Z. The method according to embodiment Q, wherein the reducing        occurs in the presence of at least one second metal or metal ion        having an atomic number different from that of the at least one        first metal ion.        AA. The at least one first metal product produced according to        the method of embodiment Q.        AB. The at least one first metal product according to embodiment        AA, said at least one product comprising at least one nanowire.        AC. An article comprising the at least one first metal product        according to embodiment AA.

U.S. Provisional Application No. 61/500,155, filed Jun. 23, 2011,entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES, whichis hereby incorporated by reference in its entirety, disclosed thefollowing seventeen non-limiting exemplary embodiments:

AD. A method comprising:

-   -   providing at least one compound comprising at least one first        atom and at least one second atom, said at least one first atom        comprising at least one atom from IUPAC Group 13 and said at        least one second atom comprising at least one halogen atom; and    -   reducing at least one first metal ion to at least one first        metal in the presence of the at least one first atom.        AE. The method according to embodiment AD, wherein the at least        one first metal ion comprises at least one coinage metal ion.        AF. The method according to embodiment AD, wherein the at least        one first metal ion comprises at least one ion of an element        from IUPAC Group 11.        AG. The method according to embodiment AD, wherein the at least        one first metal ion comprises at least one silver ion.        AH. The method according to embodiment AD, wherein the at least        one first atom comprises boron.        AJ. The method according to embodiment AD, wherein the at least        one second atom comprises at least one of chlorine, bromine, or        iodine.        AK. The method according to embodiment AD, wherein the at least        one second atom comprises chlorine.        AL. The method according to embodiment AD, wherein the compound        comprises at least one boron-carbon bond.        AM. The method according to embodiment AD, wherein the compound        comprises at least one boron-halogen bond.        AN. The method according to embodiment AD, wherein the compound        comprises at least one boron-carbon bond and at least one        boron-halogen bond.        AP. The method according to embodiment AD, wherein the compound        comprises dichlorophenylborane.        AQ. The method according to embodiment AD, wherein the reduction        is carried out in the presence of the at least one second atom.        AR. The method according to embodiment AD, wherein the reduction        is carried out in the presence of one or more of a protecting        agent or a polyol.        AS. The at least one first metal according to embodiment AD.        AT. At least one article comprising the at least one first metal        according to embodiment AS.        AU. The article according to embodiment AT, wherein the at least        one first metal comprises one or more nanowires, nanocubes,        nanorods, nanopyramids, or nanotubes.        AV. The article according to embodiment AT comprising at least        one of an electronic display, a touch screen, a portable        telephone, a cellular telephone, a computer display, a laptop        computer, a tablet computer, a point-of-purchase kiosk, a music        player, a television, an electronic game, an electronic book        reader, a transparent electrode, a solar cell, a light emitting        diode, an electronic device, a medical imaging device, or a        medical imaging medium.

U.S. Provisional Application No. 61/488,811, filed May 23, 2011,entitled NANOWIRE PREPARATION METHODS, COMPOSITIONS, AND ARTICLES, whichis hereby incorporated by reference in its entirety, disclosed thefollowing fourteen non-limiting exemplary embodiments:

AW. A method comprising:

-   -   providing a composition comprising an amount of at least one        organo-halide compound, said compound capable of forming at        least one carbocation and at least one halide ion; and    -   reducing at least one first metal ion to at least one first        metal in the presence of the composition.        AX. The method according to embodiment AW, wherein the at least        one carbocation comprises at least one secondary carbocation or        tertiary carbocation.        AY. The method according to embodiment AW, wherein the at least        one carbocation comprises at least one tertiary carbocation.        AZ. The method according to embodiment AW, wherein the at least        one halide ion comprises at least one chloride ion.        BA. The method according to embodiment AW, wherein the at least        one first metal ion comprises at least one element from IUPAC        Group 11.        BB. The method according to embodiment AW, wherein the at least        one first metal ion comprises at least one coinage metal ion.        BC. The method according to embodiment AW, wherein the at least        one first metal ion comprises at least one silver ion.        BD. The method according to embodiment AW, wherein the at least        one organo-halide compound comprises a carbon atom bonded to at        least one halogen atom, said carbon atom being also bonded to at        least one aromatic ring by at least one carbon-carbon bond.        BE. The method according to embodiment AW, wherein the at least        one organo-halide compound comprises a carbon atom bonded to at        least one halogen atom, said carbon atom being also bonded to at        least two aromatic rings by at least two carbon-carbon bonds.        BF. The method according to embodiment AW, wherein the at least        one organo-halide compound comprises triphenylchloromethane.        BG. The method according to embodiment AW, further comprising:    -   regulating the rate of halide generation by at least one of        choosing the at least one organo-halide compound, selecting the        amount of the at least one organo-halide compound in the        composition, or selecting at least one temperature at which to        perform the reduction.        BH. The at least one first metal product produced according to        the method of embodiment AW.        BJ. The at least one first metal product according to embodiment        BH, said at least one product comprising at least one nanowire.        BK. An article comprising the at least one first metal product        according to embodiment BH.

EXAMPLES Example 1

To a 500 mL reaction flask containing 280 mL ethylene glycol (EG), 0.20g of a freshly prepared 52 mM solution of diethyldichlorosilane in EGand 3.3 g of a 3 mM solution of iron (II) acetylacetone in ethyleneglycol (EG) were added. The solution was stripped of at least somedissolved gases by bubbling N₂ into the solution for at least 2 hrsusing a glass pipette at room temperature with mechanical stirring whileat 100 rpm. (This operation will be referred to as “degassing” in thesequel.) Solutions of 0.77 M polyvinylpyrrolidinone (PVP, 55,000weight-average molecular weight) in EG and 0.25 M AgNO₃ in EG weredegassed with N₂, then 20 mL syringes of each were prepared. Thereaction mixture was heated to 145° C. under N₂, then the AgNO₃ and PVPsolutions were added at a constant rate over 25 minutes via a 12 gaugeTeflon syringe needle. The reaction was held at 145° C. for 90 minutesthen allowed to cool to ambient temperature.

An optical microscope picture of the silver nanowire product is shown inFIG. 1.

Example 2

A 500 mL reaction flask containing 280 mL ethylene glycol (EG) wasdegassed with N₂ using a TEFLON® fluoropolymer tube, while stirring at100 rpm for 2 hours. To the EG was added 0.10 g of a freshly prepared0.40 M solution of phenylphosphonic dichloride in EG and 3.3 g of a 3 mMsolution of iron (II) acetylacetone in EG. The fluoropolymer tube wasthen retracted to provide nitrogen blanketing of the headspace of thereaction flask at a 0.5 L/min purge rate. Solutions of 0.84 Mpolyvinylpyrrolidinone (PVP, 55,000 weight-average molecular weight) inEG and 0.25 M AgNO₃ in EG were degassed with N₂, then 20 mL syringes ofeach were prepared. The reaction mixture was heated to 155° C. under N₂,then the AgNO₃ and PVP solutions were added at a constant rate over 25minutes via a 12 gauge a TEFLON® fluoropolymer syringe needle. Thereaction was held at 155° C. for 90 minutes, and then allowed to cool toambient temperature.

An optical microscope picture of the unpurified silver nanowire productis shown in FIG. 2.

Example 3

A 500 mL reaction flask containing 280 mL ethylene glycol (EG) wasdegassed overnight by bubbling nitrogen through its contents. To theflask, 1.3 g of freshly prepared 31 mM dichlorophenylborane in EG wasadded. The reaction mixture was heated to 145° C. under nitrogen. Stocksolutions of 0.77 M polyvinylpyrrolidinone (PVP, 55,000 weight-averagemolecular weight) in EG and 0.25 M AgNO₃ in EG were degassed withnitrogen. 20 mL syringes of the PVP and AgNO₃ solutions were preparedand then added to the reaction flask at a constant rate over 25 min viaa 12-gauge TEFLON® fluoropolymer syringe needle. The reaction mixturewas held at 145° C. for 90 min, and was then allowed to cool to ambienttemperature.

FIG. 3 shows an optical micrograph of the silver nanowire product.

Example 4

To a 500 mL reaction flask containing 280 mL ethylene glycol (EG), 2.5 gof a freshly prepared 81 mM solution of diethyldichlorosilane in EG wasadded. The solution was degassed by bubbling N₂ into the solutionovernight using a TEFLON® fluoropolymer tube at room temperature withmechanical stirring while at 100 rpm. (This operation will be referredto as “degassing” in the sequel.) Solutions of 0.84 Mpolyvinylpyrrolidinone (PVP, 55,000 weight-average molecular weight) inEG and 0.25 M AgNO₃ in EG were degassed with N₂, then 20 mL syringes ofeach were prepared. The reaction mixture was heated to 145° C. under N₂,then the AgNO₃ and PVP solutions were added at a constant rate over 25minutes via a 12 gauge TEFLON® fluoropolymer syringe needle. Thereaction was held at 145° C. for 90 minutes then allowed to cool toambient temperature.

An optical microscope picture of the silver nanowire product is shown inFIG. 4. The nanowires had an average diameter of 64.9±16.5 nm and anaverage length of 15.5±μm, based on measurement of at least 100 wires.

Examples 5-7

The procedure of Example 4 was repeated, varying the amount andconcentration of the diethyldichlorosilane/EG catalyst solution used.The results are shown in Table I, along with the results of Example 4.The average diameters and lengths varied minimally over the range ofcatalyst solutions that were tested.

Example 8 Comparative

To a 500 mL reaction flask was added 280 mL ethylene glycol (EG) and 1.4g of a freshly prepared 15 mM IrCl₃.3H₂O dispersion in EG. This solutionwas degassed for 2 hrs by bubbling N₂ into the solution using a glasspipette at room temperature with mechanical stirring while at 100 rpm.Stock solutions of 0.25 M AgNO₃ in EG and 0.84 M polyvinylpyrrolidinone(PVP) in EG were also degassed by bubbling N₂ into the solutions for atleast 60 minutes. Two syringes were loaded with 20 mL each of the AgNO₃and PVP solutions. The reaction mixture was heated to 155° C. under N₂and the AgNO₃ and PVP solutions were added at a constant rate over 25minutes via 12 gauge TEFLON® fluoropolymer syringe needles. The reactionwas held at 155° C. for 90 minutes then allowed to cool to roomtemperature.

FIG. 5 shows the reaction mixture after 60 min of reaction. Visible arenanoparticles, microparticles, with only a few short nanowires.

Example 9 Comparative

The procedure of Example 8 was repeated, using 2.9 g of a freshlyprepared 7.0 mM dispersion of K₂IrCl₆ in EG, instead of the IrCl₃.3H₂Odispersion. The reaction was carried out at 145° C., instead of 155° C.

FIG. 6 shows the reaction mixture after 90 min of reaction. Only a fewfine nanowires are visible.

Example 10 Comparative

The procedure of Example 8 was repeated, using 2.3 g of a freshlyprepared 7.0 mM dispersion of InCl₃.4H₂O in EG, instead of theIrCl₃.3H₂O dispersion.

FIG. 7 shows the reaction mixture after 90 min of reaction. No nanowiresare visible.

Example 11 Comparative

To a 100 mL reaction flask was added 50 mL ethylene glycol (EG) and 0.29g of 7.0 mM AuCl₃ in EG. This solution was degassed for 2 hrs bybubbling N₂ into the solution using a glass pipette at room temperaturewith mechanical stirring while at 100 rpm. Stock solutions of 0.25 MAgNO₃ in EG and 0.84 M polyvinylpyrrolidinone (PVP) in EG were alsodegassed by bubbling N₂ into the solutions for at least 60 minutes. Twosyringes were loaded with 3 mL each of the AgNO₃ and PVP solutions. Thereaction mixture was heated to 145° C. under N₂ and the AgNO₃ and PVPsolutions were added at a constant rate over 25 minutes via 20 gaugeTEFLON® fluoropolymer syringe needles. The reaction was held at 145° C.for 150 minutes then allowed to cool to room temperature.

Samples taken after 15, 30, 60, 90, 120, and 150 min of reactionappeared to have only nanoparticles, but no nanowires.

Example 12 Comparative

A 500 mL reaction flask containing 300 mL ethylene glycol (EG), 2.2 gpolyvinylpyrrolidinone (PVP, 55,000 weight-average molecular weight),and 9.2 mg of hafnium tetrachloride bis(tetrahydrofuran) adduct, wasdegassed overnight at room temperature using nitrogen that wasintroduced below the liquid surface through a TEFLON® fluoropolymertube. The tube was then retracted from the liquid to provide nitrogenblanketing of the reaction flask headspace at approximately 0.5 L/min,after which the agitated flask was then heated to 145° C. A stocksolution of 0.50 M AgNO₃ in EG was also degassed with nitrogen, and thena 20 mL syringe of the degassed solution was prepared. The AgNO₃solution was then added at a constant rate over 25 min via a 12 gaugeTEFLON® fluoropolymer syringe needle. The flask was then held attemperature for 60 min, after which it was allowed to cool down toambient temperature.

FIG. 8 shows an optical micrograph of the nanowire product, which had anaverage diameter of 253.5±133.0 nm and an average length of 8.7±5.5 μm,based on measurement of 100 wires.

Example 13 Comparative

The procedure of Example 12 was repeated using 6.9 mg of zirconiumtetrachloride bis(tetrahydrofuran) adduct in place of thehafnium-containing adduct. FIG. 9 shows an optical micrograph of thesilver nanowire product, which had an average diameter of 147.3±50.0 nmand an average length of 15.6±12.0 μm, based on measurement of 100wires.

Example 14 Comparative

The procedure of Example 12 was repeated using 9.9 mg of tantalum (V)chloride. FIG. 10 shows an optical micrograph of the silver nanowireproduct, which had an average diameter of 215±119 nm and an averagelength of 10.6±6.5 μm, based on measurement of 100 wires.

Example 15

To a 500 mL reaction flask containing 280 mL ethylene glycol (EG), 7.3mg of triphenylchloromethane and 3.3 g of a 3 mM solution of iron (II)acetylacetone in ethylene glycol (EG) were added. The reaction mixturewas degassed with N₂ using a glass pipette while stirring at 100 rpm for2 hours. Solutions of 0.77 M polyvinylpyrrolidinone (PVP) in EG and 0.25M AgNO₃ in EG were degassed with N₂, then 20 mL syringes of each wereprepared. The reaction mixture was heated to 155° C. under N₂, then theAgNO₃ and PVP solutions were added at a constant rate over 25 minutesvia a 12 gauge TEFLON® fluoropolymer syringe needle. The reaction washeld at 145° C. for 90 minutes then allowed to cool to ambienttemperature.

An optical micrograph of the silver nanowire product is shown in FIG.11.

Example 16

The procedure of Example 15 was replicated, except for the use of 0.16 gof a freshly prepared 0.27 M solution of benzylchloride in EG in placeof the triphenylchloromethane. Under these conditions, silver nanowireswere observed to begin forming, however, irregularly-shaped silvernanowires then formed, which tended to agglomerate into clusters.

An optical microscope picture of the product from this reaction is shownin FIG. 12.

The invention has been described in detail with particular reference toa presently preferred embodiment, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention. The presently disclosed embodiments are thereforeconsidered in all respects to be illustrative and not restrictive. Thescope of the invention is indicated by the appended claims, and allchanges that come within the meaning and range of equivalents thereofare intended to be embraced therein.

TABLE I Et₂SiCl₂ Solution Average Average EXAMPLE Used Diameter (nm)Length (μm) 4 2.5 g of 0.81 mM 65 16 5 5.0 g of 0.81 mM 68 14 6 4.4 g of0.45 mM 62 14 7 1.0 g of 0.81 mM 60 13

1. A method comprising: providing at least one compound capable offorming at least one halide ion, said compound comprising at least onefirst atom, at least one halogen atom bonded to the at least one firstatom, and at least one carbon atom bonded to the at least one firstatom; and reducing at least one first metal ion to at least one firstmetal in the presence of at least one of the at least one compound orthe at least one halide ion, wherein the absolute value of thedifference in electronegativities of the at least one first atom and theat least one halogen atom is greater than about 0.4 Pauling units andless than about 2.0 Pauling units.
 2. The method according to claim 1,wherein the at least one first atom comprises at least one of a boronatom, a nitrogen atom, a phosphorus atom, a silicon atom, a sulfur atom,a selenium atom, or a carbon atom.
 3. The method according to claim 1,wherein the at least one first atom comprises at least one of a boronatom, a phosphorus atom, a silicon atom, or a carbon atom.
 4. The methodaccording to claim 1, further comprising forming the at least one halideion by solvolysis of the at least one compound.
 5. The method accordingto claim 1, wherein the at least one halide ion comprises at least onechloride ion or bromide ion.
 6. The method according to claim 1, whereinthe at least one compound is capable of forming at least onecarbocation.
 7. The method according to claim 1, wherein the at leastone compound comprises at least one of diethyldichlorosilane,phenylphosphonic dichloride, dichlorophenylborane, ortriphenylmethylchloride.
 8. The method according to claim 1, wherein theat least one first metal comprises at least one element from IUPAC Group11 or at least one coinage metal.
 9. The method according to claim 1,wherein the at least one first metal comprises silver.
 10. At least onenanowire comprising the at least one first metal produced according tothe method of claim 1.